<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
    <style>
      *{
        margin: 0;
        padding: 0;
      }
      .box{
        width: 60%;
        height:98vh;
        border: 1px solid firebrick;
        margin: 0 auto;

        display: flex;
        flex-direction: column;
      }
      .header{
        height: 45px;
        background-color: #87CEEB;
        text-align: center;
        line-height: 45px;

      }
      .main .side{
        flex: 1;
        background-color: #CCCCCC;
       
       /* 文字居中 */
       display: flex;
       justify-content: center;
       align-items: center;
       
        
      }
      .main .content{
        flex: 2;
        background-color: aqua;
       
       
       display: flex;
       justify-content: center;
       align-items: center;
       
        
      }
      .main{
        /* 平分 */
         flex: 1;

         display: flex;
         flex-direction: row;
      }
      .footer{
       height: 30px;
       background-color: rosybrown;
       text-align: center;
       line-height: 30px;
       color: #FFFFFF;
      }
    </style>
	</head>
	<body>
    <div class="box">
      <div class="header">头部</div>
      <div class="main">
        <div class="side">侧边栏</div>
        <div class="content">主题内容</div>
      </div>
      <div class="footer"></div>
    </div>
	</body>
</html>
